$\begin{cases} f(1)=-6 \\\\ f(2)=-4 \\\\ f(n)=f(n-2) + f(n-1) \end{cases}$ $f(3)=$
Explanation: ${f(3)}={f(1)}+{f(2)}=({-6})+({-4})={-10}$ $f(3)=-10$